[RFC] remove highmem_start_page

From: Dave Hansen
Date: Tue Oct 26 2004 - 15:06:13 EST

People love to do comparisons with highmem_start_page. However, where
CONFIG_HIGHMEM=y and there is no actual highmem, there's no real page
at *highmem_start_page.

That's usually not a problem, but CONFIG_NONLINEAR is a bit more strict
and catches the bogus address tranlations.

There are about a gillion different ways to find out of a 'struct page'
is highmem or not. Why not just check page_flags?

Declare page_is_highmem() and use it wherever there used to be a
highmem_start_page comparison. Then, kill off highmem_start_page.

memhotplug-dave/arch/i386/mm/discontig.c | 4 ----
memhotplug-dave/arch/i386/mm/highmem.c | 6 +++---
memhotplug-dave/arch/i386/mm/init.c | 1 -
memhotplug-dave/arch/i386/mm/pageattr.c | 5 +----
memhotplug-dave/arch/mips/mm/highmem.c | 6 +++---
memhotplug-dave/arch/mips/mm/init.c | 1 -
memhotplug-dave/arch/ppc/mm/init.c | 1 -
memhotplug-dave/arch/sparc/mm/highmem.c | 2 +-
memhotplug-dave/arch/sparc/mm/init.c | 2 --
memhotplug-dave/arch/um/kernel/mem.c | 5 -----
memhotplug-dave/include/asm-ppc/highmem.h | 6 +++---
memhotplug-dave/include/asm-sparc/highmem.h | 4 ++--
memhotplug-dave/include/linux/highmem.h | 12 ++++++++++--
memhotplug-dave/mm/memory.c | 2 --
memhotplug-dave/net/core/dev.c | 2 +-
15 files changed, 24 insertions(+), 35 deletions(-)

-- Dave

People love to do comparisons with highmem_start_page. However, where
CONFIG_HIGHMEM=y and there is no actual highmem, there's no real page
at *highmem_start_page.

That's usually not a problem, but CONFIG_NONLINEAR is a bit more strict
and catches the bogus address tranlations.

There are about a gillion different ways to find out of a 'struct page'
is highmem or not. Why not just check page_flags?

Declare page_is_highmem() and use it wherever there used to be a
highmem_start_page comparison. Then, kill off highmem_start_page.

This removes more code than it adds, and gets rid of some nasty
#ifdefs in .c files.

Signed-off-by: Dave Hansen <haveblue@xxxxxxxxxx>
---

memhotplug-dave/arch/i386/mm/discontig.c | 4 ----
memhotplug-dave/arch/i386/mm/highmem.c | 6 +++---
memhotplug-dave/arch/i386/mm/init.c | 1 -
memhotplug-dave/arch/i386/mm/pageattr.c | 5 +----
memhotplug-dave/arch/mips/mm/highmem.c | 6 +++---
memhotplug-dave/arch/mips/mm/init.c | 1 -
memhotplug-dave/arch/ppc/mm/init.c | 1 -
memhotplug-dave/arch/sparc/mm/highmem.c | 2 +-
memhotplug-dave/arch/sparc/mm/init.c | 2 --
memhotplug-dave/arch/um/kernel/mem.c | 5 -----
memhotplug-dave/include/asm-ppc/highmem.h | 6 +++---
memhotplug-dave/include/asm-sparc/highmem.h | 4 ++--
memhotplug-dave/include/linux/highmem.h | 12 ++++++++++--
memhotplug-dave/mm/memory.c | 2 --
memhotplug-dave/net/core/dev.c | 2 +-
15 files changed, 24 insertions(+), 35 deletions(-)

diff -puN arch/i386/lib/kgdb_serial.c~A1-no-highmem-mess arch/i386/lib/kgdb_serial.c
diff -puN arch/i386/mm/discontig.c~A1-no-highmem-mess arch/i386/mm/discontig.c
--- memhotplug/arch/i386/mm/discontig.c~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/arch/i386/mm/discontig.c 2004-10-26 12:50:02.000000000 -0700
@@ -465,10 +465,6 @@ void __init set_max_mapnr_init(void)
{
#ifdef CONFIG_HIGHMEM
struct zone *high0 = &NODE_DATA(0)->node_zones[ZONE_HIGHMEM];
- if (high0->spanned_pages > 0)
- highmem_start_page = high0->zone_mem_map;
- else
- highmem_start_page = pfn_to_page(max_low_pfn+1);
num_physpages = highend_pfn;
#else
num_physpages = max_low_pfn;
diff -puN arch/mips/mm/highmem.c~A1-no-highmem-mess arch/mips/mm/highmem.c
--- memhotplug/arch/mips/mm/highmem.c~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/arch/mips/mm/highmem.c 2004-10-26 12:50:02.000000000 -0700
@@ -8,7 +8,7 @@ void *__kmap(struct page *page)
void *addr;

might_sleep();
- if (page < highmem_start_page)
+ if (!page_is_highmem(page))
return page_address(page);
addr = kmap_high(page);
flush_tlb_one((unsigned long)addr);
@@ -20,7 +20,7 @@ void __kunmap(struct page *page)
{
if (in_interrupt())
BUG();
- if (page < highmem_start_page)
+ if (!page_is_highmem(page))
return;
kunmap_high(page);
}
@@ -41,7 +41,7 @@ void *__kmap_atomic(struct page *page, e

/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
inc_preempt_count();
- if (page < highmem_start_page)
+ if (!page_is_highmem(page))
return page_address(page);

idx = type + KM_TYPE_NR*smp_processor_id();
diff -puN arch/um/kernel/mem.c~A1-no-highmem-mess arch/um/kernel/mem.c
--- memhotplug/arch/um/kernel/mem.c~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/arch/um/kernel/mem.c 2004-10-26 12:50:02.000000000 -0700
@@ -49,8 +49,6 @@ static void setup_highmem(unsigned long
unsigned long highmem_pfn;
int i;

- highmem_start_page = virt_to_page(highmem_start);
-
highmem_pfn = __pa(highmem_start) >> PAGE_SHIFT;
for(i = 0; i < highmem_len >> PAGE_SHIFT; i++){
page = &mem_map[highmem_pfn + i];
@@ -67,9 +65,6 @@ void mem_init(void)
unsigned long start;

max_low_pfn = (high_physmem - uml_physmem) >> PAGE_SHIFT;
-#ifdef CONFIG_HIGHMEM
- highmem_start_page = phys_page(__pa(high_physmem));
-#endif

/* clear the zero-page */
memset((void *) empty_zero_page, 0, PAGE_SIZE);
diff -puN include/asm-sparc/highmem.h~A1-no-highmem-mess include/asm-sparc/highmem.h
--- memhotplug/include/asm-sparc/highmem.h~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/include/asm-sparc/highmem.h 2004-10-26 12:50:02.000000000 -0700
@@ -57,7 +57,7 @@ extern void kunmap_high(struct page *pag
static inline void *kmap(struct page *page)
{
BUG_ON(in_interrupt());
- if (page < highmem_start_page)
+ if (!page_is_highmem(page))
return page_address(page);
return kmap_high(page);
}
@@ -65,7 +65,7 @@ static inline void *kmap(struct page *pa
static inline void kunmap(struct page *page)
{
BUG_ON(in_interrupt());
- if (page < highmem_start_page)
+ if (!page_is_highmem(page))
return;
kunmap_high(page);
}
diff -puN include/linux/highmem.h~A1-no-highmem-mess include/linux/highmem.h
--- memhotplug/include/linux/highmem.h~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/include/linux/highmem.h 2004-10-26 12:53:28.000000000 -0700
@@ -9,13 +9,16 @@

#ifdef CONFIG_HIGHMEM

-extern struct page *highmem_start_page;
-
#include <asm/highmem.h>

/* declarations for linux/mm/highmem.c */
unsigned int nr_free_highpages(void);

+static inline int page_is_highmem(struct page *page)
+{
+ return PageHighMem(page);
+}
+
#else /* CONFIG_HIGHMEM */

static inline unsigned int nr_free_highpages(void) { return 0; }
@@ -33,6 +36,11 @@ static inline void *kmap(struct page *pa
#define kmap_atomic_pfn(pfn, idx) page_address(pfn_to_page(pfn))
#define kmap_atomic_to_page(ptr) virt_to_page(ptr)

+static inline int page_is_highmem(struct page *page)
+{
+ return 0;
+}
+
#endif /* CONFIG_HIGHMEM */

/* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
diff -puN net/core/dev.c~A1-no-highmem-mess net/core/dev.c
--- memhotplug/net/core/dev.c~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/net/core/dev.c 2004-10-26 12:50:02.000000000 -0700
@@ -1152,7 +1152,7 @@ static inline int illegal_highdma(struct
return 0;

for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
- if (skb_shinfo(skb)->frags[i].page >= highmem_start_page)
+ if (page_is_highmem(skb_shinfo(skb)->frags[i].page))
return 1;

return 0;
diff -puN arch/sparc/mm/highmem.c~A1-no-highmem-mess arch/sparc/mm/highmem.c
--- memhotplug/arch/sparc/mm/highmem.c~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/arch/sparc/mm/highmem.c 2004-10-26 12:50:02.000000000 -0700
@@ -36,7 +36,7 @@ void *kmap_atomic(struct page *page, enu

/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
inc_preempt_count();
- if (page < highmem_start_page)
+ if (!page_is_highmem(page))
return page_address(page);

idx = type + KM_TYPE_NR*smp_processor_id();
diff -puN arch/sparc/mm/init.c~A1-no-highmem-mess arch/sparc/mm/init.c
--- memhotplug/arch/sparc/mm/init.c~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/arch/sparc/mm/init.c 2004-10-26 12:50:02.000000000 -0700
@@ -402,8 +402,6 @@ void __init mem_init(void)
int reservedpages = 0;
int i;

- highmem_start_page = pfn_to_page(highstart_pfn);
-
if (PKMAP_BASE+LAST_PKMAP*PAGE_SIZE >= FIXADDR_START) {
prom_printf("BUG: fixmap and pkmap areas overlap\n");
prom_printf("pkbase: 0x%lx pkend: 0x%lx fixstart 0x%lx\n",
diff -puN arch/ppc/mm/init.c~A1-no-highmem-mess arch/ppc/mm/init.c
--- memhotplug/arch/ppc/mm/init.c~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/arch/ppc/mm/init.c 2004-10-26 12:50:02.000000000 -0700
@@ -411,7 +411,6 @@ void __init mem_init(void)
unsigned long highmem_mapnr;

highmem_mapnr = total_lowmem >> PAGE_SHIFT;
- highmem_start_page = mem_map + highmem_mapnr;
#endif /* CONFIG_HIGHMEM */
max_mapnr = total_memory >> PAGE_SHIFT;

diff -puN arch/i386/mm/pageattr.c~A1-no-highmem-mess arch/i386/mm/pageattr.c
--- memhotplug/arch/i386/mm/pageattr.c~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/arch/i386/mm/pageattr.c 2004-10-26 12:50:02.000000000 -0700
@@ -105,10 +105,7 @@ __change_page_attr(struct page *page, pg
unsigned long address;
struct page *kpte_page;

-#ifdef CONFIG_HIGHMEM
- if (page >= highmem_start_page)
- BUG();
-#endif
+ BUG_ON(page_is_highmem(page));
address = (unsigned long)page_address(page);

kpte = lookup_address(address);
diff -puN arch/i386/mm/highmem.c~A1-no-highmem-mess arch/i386/mm/highmem.c
--- memhotplug/arch/i386/mm/highmem.c~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/arch/i386/mm/highmem.c 2004-10-26 12:50:02.000000000 -0700
@@ -3,7 +3,7 @@
void *kmap(struct page *page)
{
might_sleep();
- if (page < highmem_start_page)
+ if (!page_is_highmem(page))
return page_address(page);
return kmap_high(page);
}
@@ -12,7 +12,7 @@ void kunmap(struct page *page)
{
if (in_interrupt())
BUG();
- if (page < highmem_start_page)
+ if (!page_is_highmem(page))
return;
kunmap_high(page);
}
@@ -32,7 +32,7 @@ void *kmap_atomic(struct page *page, enu

/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
inc_preempt_count();
- if (page < highmem_start_page)
+ if (!page_is_highmem(page))
return page_address(page);

idx = type + KM_TYPE_NR*smp_processor_id();
diff -puN arch/mips/mm/init.c~A1-no-highmem-mess arch/mips/mm/init.c
--- memhotplug/arch/mips/mm/init.c~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/arch/mips/mm/init.c 2004-10-26 12:50:02.000000000 -0700
@@ -204,7 +204,6 @@ void __init mem_init(void)
unsigned long tmp, ram;

#ifdef CONFIG_HIGHMEM
- highmem_start_page = mem_map + highstart_pfn;
#ifdef CONFIG_DISCONTIGMEM
#error "CONFIG_HIGHMEM and CONFIG_DISCONTIGMEM dont work together yet"
#endif
diff -puN include/asm-ppc/highmem.h~A1-no-highmem-mess include/asm-ppc/highmem.h
--- memhotplug/include/asm-ppc/highmem.h~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/include/asm-ppc/highmem.h 2004-10-26 12:50:02.000000000 -0700
@@ -56,7 +56,7 @@ extern void kunmap_high(struct page *pag
static inline void *kmap(struct page *page)
{
might_sleep();
- if (page < highmem_start_page)
+ if (!page_is_highmem(page))
return page_address(page);
return kmap_high(page);
}
@@ -64,7 +64,7 @@ static inline void *kmap(struct page *pa
static inline void kunmap(struct page *page)
{
BUG_ON(in_interrupt());
- if (page < highmem_start_page)
+ if (!page_is_highmem(page))
return;
kunmap_high(page);
}
@@ -82,7 +82,7 @@ static inline void *kmap_atomic(struct p

/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
inc_preempt_count();
- if (page < highmem_start_page)
+ if (!page_is_highmem(page))
return page_address(page);

idx = type + KM_TYPE_NR*smp_processor_id();
diff -puN mm/memory.c~A1-no-highmem-mess mm/memory.c
--- memhotplug/mm/memory.c~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/mm/memory.c 2004-10-26 12:50:02.000000000 -0700
@@ -74,11 +74,9 @@ unsigned long num_physpages;
* and ZONE_HIGHMEM.
*/
void * high_memory;
-struct page *highmem_start_page;
unsigned long vmalloc_earlyreserve;

EXPORT_SYMBOL(num_physpages);
-EXPORT_SYMBOL(highmem_start_page);
EXPORT_SYMBOL(high_memory);
EXPORT_SYMBOL(vmalloc_earlyreserve);

diff -puN arch/i386/mm/init.c~A1-no-highmem-mess arch/i386/mm/init.c
--- memhotplug/arch/i386/mm/init.c~A1-no-highmem-mess 2004-10-26 12:50:02.000000000 -0700
+++ memhotplug-dave/arch/i386/mm/init.c 2004-10-26 12:50:02.000000000 -0700
@@ -568,7 +568,6 @@ void __init test_wp_bit(void)
static void __init set_max_mapnr_init(void)
{
#ifdef CONFIG_HIGHMEM
- highmem_start_page = pfn_to_page(highstart_pfn);
max_mapnr = num_physpages = highend_pfn;
#else
max_mapnr = num_physpages = max_low_pfn;
_